1. Field of the Invention
The invention relates to a continuously working press, and, more particularly, to a continuously working press for the production of chipboards, fiberboard, plastic boards, plywood boards or the like.
Such presses typically include flexible, endless steel bands which transmit the pressing force and draw the article to be pressed through the press and which are supported with an adjustable press nip against abutments of a press platen and a press ram via co-rotating rolling rods guided with their axes transverse relative to the running direction of the band. The rolling rods are typically introduced in the entry region orthogonally relative to the longitudinal center of the press and into the pressing region by plate-link chains and by introduction devices.
2. Discussion of the Related Art
In the known press according to German patent specification No. 3,152,911, (see U.S. Pat. No. 4,480,978), the introduction device consists of a plurality of rotating roller chains which are distributed at a distance from one another over the width of the sheet-steel press bands, the rolling rods being mounted in the entry region in the manner of rolling bearings on the rollers of the roller chains.
A disadvantage of this rolling-rod introduction device is that, when the rolling rods are permanently aligned at an exact distance from one another, an overloading of the roller chains and consequently a differing extension of the chainlink plates occur. As a result of this the rolling rods are no longer at an exact distance from one another during the entry into the high-pressure region. A run-on of the rolling rods and their destruction could be the consequence. Furthermore, the directing forces of the rollers which act permanently on the rolling rods give rise to a partial wear on the rolling rods and in the joints of the roller chains. The wear in the joints results in a greater play. But because of this, an exact alignment of the rolling rods which occurs when a predetermined distance between them being maintained, is lost. This is because, with increasing age, the roller chains have a different pitch division, and therefore, the alignment of the rolling rods with an exact gap spacing depends on the counterpressure resulting from the article to be pressed.
Another disadvantage is that the roller chains cool during the return outside of the heating plates. At different temperatures between the two outer chain introduction points (on the left and right), an orthogonal entry is thus disrupted by different chain extensions caused by thermal expansion of the roller chains. Moreover, in the region of positive introduction beginning from the start of the entry tangent, the roller chains undergo an elongation as a result of an increase of temperature. This elongation partially brings about a higher rolling speed in this region than the usual speed of 0.5.times.the steel-band speed. This partial acceleration likewise leads to wear on the roller chains and rolling rods, creating a further adverse effect on the surface of the pressed boards from striation.